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Lecture 13: Global Illumination & Path Tracing (39)
yinxudeng
  1. Are L_o on the left and L_o on the right the same?

  2. Why do we need (R composite T) instead of just T?

joshua16266261
  1. I believe they are the same. I think this is where the recursion comes from.

  2. We need RTR \circ T because T(Lo)(p,ωi)T(L_o)(p, \omega_i) is just Lo(tr(p,ωi),ωi)L_o (tr(p, \omega_i), - \omega_i). To get the integral, we then need to apply RR to T(Lo)T(L_o).

JefferyYC

Applying T is equivalent to finding the surface point that L_o first touches and inverse its direction. We then apply R, which means integrating every inverse ray that would be reflected in the direction of w_o, and then reflect it. So overall we simply integrate every ray coming from different surface points that bounces in the direction of w_o.

phoebeli23

What is the difference between outgoing and emitted light? (Lo and Le)

cchendyc

Le (light source in this case) is handling the light emitting from the pixel other than from or related to p, whereas Lo is out wrt the ray in direction of -wi, which was originated from p in direction w_i

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